L78M00AB/AC SERIES

12/17

APPLICATIONS INFORMATION

DESIGN CONSIDERATIONS

The L78M00AB Series of fixed voltage regulators are designed with Thermal Overload Protection that

shuts down the circuit when subjected to an excessive power overload condition, Internal Short-Circuit

Protection that limits the maximum current the circuit will pass, and Output Transistor Safe-Area

Compensation that reduces the output short-circuit as the voltage across the pass transistor is increased.

In many low current applications, compensation capacitors are not required. However, it is recommended

that the regulator input be bypassed with a capacitor if the regulator is connected to the power supply filter

with long wire lengths, or if the output load capacitance is large. An input bypass capacitor should be

selected to provide good high-frequency characteristics to insure stable operation under all load

conditions. A 0.33µF or larger tantalum, mylar, or other capacitor having low internal impedance at high

frequencies should be chosen. The bypass capacitor should be mounted with the shortest possible leads

directly across the regulators input terminals. Normally good construction techniques should be used to

minimize ground loops and lead resistance drops since the regulator has no external sense lead.

Figure 13 : Current Regulator

Figure 14 : Adjustable Output Regulator

The addition of an operational amplifier allows adjustment to higher or intermediate values while retaining regulation characteristics. The min-

imum voltage obtainable with this arrangement is 2.0V greater than the regulator voltage.